The present invention relates to a cutting member and a method of manufacturing such a cutting member of compacted powder.
It is conventional to form a chipforming cutting insert of a compacted powder body which comprises a binder material and a hard material such as metal carbides, metal nitrides or ceramic material. The body is substantially disc-shaped and comprises an upper face, a lower face and at least one side surface connecting the upper and lower faces. The upper face is oriented at an acute angle with each side surface to form a cutting edge.
Heretofore, it has been practical to employ a powder-compacting technique to form single-sided inserts of the type described above. However, due to the complicated insert geometry of invertible inserts, it has not previously been practically possible to use conventional press tools for pressing such inserts of the invertible type, i.e., inserts having a double-positive geometry. By double-positive geometry is meant an insert whose upper and lower faces intersect the side faces at an acute angle to form cutting edges on both faces. That is, if such double-positive inserts were directly pressed in conventional press tools it would not be possible, without causing damage, to remove the powder body from the pressing tool after completion of the pressing.
In French Patent Application No. 1,522,955 a method of assembling two portions made of sintered metal powder is described. In accordance with that method two pieces are provided with compatible protrusions and recesses and the pieces are pressed and brazed together such that the protrusions and recesses become locked together by plastic deformation. Those two pieces are not identical in shape and therefore two different types for press tools must be used to their manufacture which makes this method time-consuming. Time-consumption is exacerbated due to the fact that braze material is introduced between the pieces before pressing takes place. That method cannot be used for assembling two powder bodies of hard material due to their brittleness prior to sintering. That is, the plastic deformation will create inner stresses in the material which are objectionable in the case of cemented carbide material for example, due to the small resistance to tensile stresses that is a typical characteristic of cemented carbide.
It is therefore an object of the present invention to enable a cutting member to be easily be produced by powder compaction.
It is another object of the invention to provide such a member which is useful as a blank for making a cutting insert.
It is another object to provide a double-sided cutting insert which inherently has necessary clearance angles.
It is another object of the invention to provide a simple method for the manufacture of a cutting insert having a complicated geometry.